Vehicle disc brake

ABSTRACT

The present invention is a vehicle disc brake for which incorrect installation of a friction pad can be prevented with a simple structure. The disc brake is provided with incorrect installation-preventing parts with which, if a friction pad ( 4 ) is installed with an incorrect installation orientation when a pair of tabs ( 10, 11 ) provided on the disc entry-side and disc exit-side of the back plate ( 4   d ) of a friction pad ( 4 ) is installed into pad guide grooves ( 9 ) formed on a caliper body ( 3 ), the tabs bump into the caliper body ( 3 ) and prevent the incorrect installation. The incorrect installation-preventing parts are formed from caliper-side recesses ( 9   d,    9   e ), which are formed in the pad guide grooves ( 9 ) towards the center of the caliper body, and tab-side protrusions ( 10   a,    11   a ), which have shapes that correspond to the caliper-side recesses ( 9   d,    9   e ).

This application is a divisional application of U.S. application Ser.No. 15/538,997, filed on Jun. 22, 2017, now U.S. Pat. No. 11,098,772,which is a National Stage of International Application No.PCT/JP2015/084933, filed on Dec. 14, 2015 and claims priority toJapanese Patent Applications No. 2014-261903 filed on Dec. 25, 2014 andNo. 2015-211664 filed on Oct. 28, 2015, the disclosure of which arehereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a vehicle disc brake and, moreparticularly, to a vehicle disc brake in which a pair of tabs providedon friction pads are housed in pad guide grooves formed in a caliperbody and the friction pads are supported movably in a disc axialdirection.

BACKGROUND ART

Conventionally, there is a vehicle disc brake that has a caliper bodyprovided with acting parts having cylinder holes opened toward a discrotor and a pair of friction pads disposed on both sides of the discrotor, in which each of the friction pads has a pair of tabs on the discentry side and the disc exit side of the back plates of the frictionpads in forward travel of the vehicle and the friction pads aresupported movably in a disc axial direction by housing the tabs in padguide grooves formed in a caliper body (see, for example, PTL 1).

CITATION LIST Patent Literature

PTL 1: JP-A-2014-74500

SUMMARY OF INVENTION Technical Problem

Although FIG. 8 of PTL 1 above illustrates the installation of afriction pad (brake pad 80) in a caliper body 72, the friction pad canalso be installed in the caliper body with the friction pad reversed,possibly causing so-called incorrect installation. FIG. 11 easilyillustrates the problem with incorrect installation. As is clear fromthe disc brake illustrated in FIG. 11, even in the state in which thedisc outer circumferential side and the disc inner circumferential sideof a friction pad 61 are reversed, tabs 62 and 62 of the friction pad 61can be inserted into pad guide grooves 64 and 64 provided in a caliperbody 63, as illustrated in dashed lines.

An object of the invention is to provide a vehicle disc brake capable ofpreventing the incorrect installation of friction pads using a simplestructure.

Solution to Problem

To achieve the above object, the vehicle disc brake according to theinvention includes a caliper body provided with an acting part having acylinder hole open toward a disc rotor and a pair of friction padsdisposed on both sides of the disc rotor, each of the friction padshaving a pair of tabs on a disc entry side and a disc exit side inforward travel of a vehicle, the friction pads being supported movablyin a disc axial direction by housing the tabs in pad guide groovesformed in a caliper body, in which an incorrect installation preventingpart is provided so as to prevent incorrect installation by bumpingagainst the caliper body or the tabs when the friction pads areinstalled in the pad guide grooves in an incorrect orientation.

In addition, preferably, the incorrect installation preventing part isformed by a caliper side recess or a caliper side protrusion formed ineach of the pad guide grooves and a tab side protrusion having a shapecorresponding to the caliper side recess or a tab side recess having ashape corresponding to the caliper side protrusion formed in each of thetabs and, when the friction pads are installed in the incorrectorientation, the caliper side protrusion bumps against the tab or thetab side protrusion bumps against the pad guide groove.

In addition, preferably, the incorrect installation preventing part isformed by a protrusion protruding in a disc rotor circumferentialdirection, the protrusion being provided in a disc radial directioninner side end of the disc exit side surface or the disc entry sidesurface of each of the friction pads in forward travel of the vehicle,and the protrusion bumps against the caliper body when the friction padsare installed in the incorrect orientation.

In addition, preferably, the incorrect installation preventing part isformed by a pair of protrusions protruding in a disc rotorcircumferential direction, the protrusions being provided in the discradial direction inner side end of the disc exit side surface or thedisc entry side surface of each of the friction pads in forward travelof the vehicle, and the protrusions bump against the caliper body whenthe friction pads are installed in the incorrect orientation.

In addition, preferably, the vehicle disc brake includes a caliper bodyprovided with an acting part having a cylinder hole open toward a discrotor, the acting part having a torque reception part making contactwith a disc exit side surface or a disc entry side surface of each ofthe friction pads in forward travel of a vehicle and receiving a brakingtorque, pad guide grooves are provided in an intermediate part in a discradial direction of the torque reception part and a pair of frictionpads disposed on both sides of the disc rotor, each of the friction padshaving a pair of tabs on a disc entry side and a disc exit side of aback plate in forward travel of the vehicle, the friction pads beingsupported movably in a disc axial direction by housing the tabs in padguide grooves, in which the friction pads are formed to have differentwidths from the disc exit side surface to the disc entry side surface ofthe back plate in forward travel of the vehicle between an outer sideand an inner side in the disc radial direction of the tabs, the torquereception part is formed to have different lengths between the torquereception parts facing each other across the friction pads so as tocorrespond to the shape of the back plate between the outer side and theinner side in the disc radial direction of the pad guide grooves, andthe back plate bumps against the caliper body when the friction pads areinstalled in an incorrect orientation.

In addition, preferably, the vehicle disc brake includes a caliper bodyprovided with an acting part having a cylinder hole open toward a discrotor and a bridge part straddling an outer circumference of the discrotor, the acting part having a torque reception part making contactwith a disc exit side surface or a disc entry side surface of each ofthe friction pads in forward travel of a vehicle and receiving a brakingtorque, pad guide grooves are provided in an intermediate part in a discradial direction of the torque reception part and a pair of frictionpads disposed on both sides of the disc rotor, each of the friction padshaving a pair of tabs on a disc entry side and a disc exit side of aback plate in forward travel of the vehicle, the friction pads beingsupported movably in a disc axial direction by housing the tabs in padguide grooves, in which, when the friction pads are installed with adisc inner circumferential side and a disc outer circumferential sidereversed by mistake, the tab are formed on the outer side in the discradial direction of the back plate and the pad guide grooves are formedon the outer side in the disc radial direction of the torque receptionpart so that the disc inner circumferential side of the friction padsbumps against an inner surface of the bridge part.

Advantageous Effects of Invention

In the vehicle disc brake according to the invention, if the frictionpads are installed in the caliper body in an incorrect orientation, thetabs of the friction pads cannot be inserted into the pad guide groovesdue to a bump against the incorrect installation preventing part,thereby preventing incorrect installation.

In addition, the incorrect installation preventing part is formed by thecaliper side recesses or the caliper side protrusions formed in the padguide grooves and the tab side protrusions or the tab side recesses,formed in the tabs, that have shapes corresponding to the caliper siderecesses or the caliper side protrusions. Accordingly, when the frictionpads are installed in the correct state, the friction pads can beinstalled to the caliper body by inserting the tab side protrusions intothe caliper side recesses or inserting the caliper side protrusions intothe tab side recesses and inserting the tabs of the friction pads intothe pad guide grooves. In contrast, when an attempt is made to installthe friction pads with the disc outer circumferential side and the discinner circumferential side reversed by mistake, the caliper sideprotrusions bump against the tabs or the tab side protrusions bumpagainst the pad guide grooves and the tabs cannot be inserted into thepad guide grooves, thereby preventing the incorrect installation of thefriction pads.

In addition, since the incorrect installation preventing part is formedby the protrusion, protruding in the disc rotor circumferentialdirection, that is provided at the disc radial direction inner side endof the disc exit side surface or the disc entry side surface of thefriction pads in forward travel of the vehicle, the protrusions formedon the friction pads are disposed closer to the disc entry side than thecaliper body when the friction pads are installed in the correct stateand the friction pads can be installed to the caliper body withoutbumping against the caliper body. In contrast, when an attempt is madeto install the friction pads with the disc outer circumferential sideand the disc inner circumferential side reversed by mistake, theprotrusions bump against the caliper body and the friction pads cannotbe installed to the caliper body, thereby preventing incorrectinstallation.

In addition, since the incorrect installation preventing part is formedby a pair of protrusions, protruding in the disc rotor circumferentialdirection, that is provided at the disc radial direction inner side endof the disc exit side surface and the disc entry side surface in forwardtravel of a vehicle, the protrusions formed on the friction pads aredisposed closer to the disc entry side than the caliper body when thefriction pads are installed in the correct state, so the friction padscan be installed to the caliper body without bumping against the caliperbody. In contrast, when an attempt is made to install the friction padswith the disc outer circumferential side and the disc innercircumferential side reversed by mistake, the pair of protrusions bumpagainst the caliper body and the friction pads cannot be installed tothe caliper body, thereby preventing incorrect installation. Inaddition, since the protrusions are provided in two positions (the discexit side surface and the disc entry side surface), even when an attemptis made to insert the tabs into the pad guide grooves in the state inwhich the disc outer circumferential side and the disc innercircumferential side of the friction pads are reversed and the tabs areinclined obliquely with respect to the caliper body, any of theprotrusions bumps against the caliper body and incorrect installationcan be surely prevented. In addition, since the amount of exposure fromthe caliper body can be reduced by reducing the height of theprotrusions, the appearance can be kept good by making the protrusionsinconspicuous.

In addition, in back plates of the friction pads, the width between thedisc exit side surface and the disc entry side surface in forward travelof the vehicle is different between the outer side in the disc radialdirection of the tabs and the inner side in the disc radial direction ofthe tabs, the pad guide grooves are provided in an intermediate part inthe disc radial direction of the torque reception parts, and the lengthbetween the torque reception parts facing each other across frictionpads is different between the outer side in the disc radial direction ofthe pad guide grooves and the inner side in the disc radial direction ofthe pad guide grooves, so the friction pads can be installedappropriately because the shapes of the torque reception partscorrespond to the shapes of the back plates of the friction pads whenthe friction pads are installed in the correct state. In contrast, whenan attempt is made to install the friction pads with the disc outercircumferential side and the disc inner circumferential side reversed bymistake, the part having a large width from the disc exit side surfaceto the disc entry side surface of the back plate makes contact with thecaliper body in the part having a small length between the torquereception parts facing each other across the friction pad and thefriction pads cannot be installed to the caliper body, therebypreventing incorrect installation.

In addition, the tabs are formed on the outer side in the disc radialdirection of the back plate and the pad guide grooves are formed on theouter side in the disc radial direction of the torque reception part sothat the disc inner circumferential side of the friction pad bumpsagainst the bridge part of the caliper body when the friction pads areinstalled with the disc outer circumferential side and the disc innercircumferential side reversed by mistake, so the appearance can be keptgood while preventing incorrect installation with a simple structure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view illustrating the front of a vehicledisc brake according to a first embodiment of the invention.

FIG. 2 is an explanatory diagram illustrating a case in which an attemptis made to install a friction pad with a disc outer circumferential sideand a disc inner circumferential side reversed.

FIG. 3 is a cross sectional view taken along line in FIG. 1 .

FIG. 4 is a cross sectional view illustrating the front of a vehicledisc brake according to a second embodiment of the invention.

FIG. 5 is an explanatory diagram illustrating a case in which an attemptis made to install a friction pad according to the second embodimentwith a disc outer circumferential side and a disc inner circumferentialside reversed.

FIG. 6 is a cross sectional view illustrating the front of a vehicledisc brake according to a third embodiment of the invention.

FIG. 7 is an explanatory diagram illustrating a case in which an attemptis made to install a friction pad according to the third embodiment witha disc outer circumferential side and a disc inner circumferential sidereversed.

FIG. 8 is a cross sectional view illustrating the front of a vehicledisc brake according to a fourth embodiment of the invention.

FIG. 9 is an explanatory diagram illustrating a case in which an attemptis made to install a friction pad according to the fourth embodimentwith a disc outer circumferential side and a disc inner circumferentialside reversed.

FIG. 10 is a cross sectional view illustrating the front of the vehicledisc brake according to the fourth embodiment of the invention.

FIG. 11 is an explanatory diagram illustrating a conventional vehicledisc brake.

FIG. 12 is a cross sectional view illustrating a front of a vehicle discbrake according to a modified embodiment.

FIG. 13 is an explanatory diagram illustrating a case in which anattempt is made to install a friction pad with a disc outercircumferential side and a disc inner circumferential side reversedaccording to the modified embodiment.

DESCRIPTION OF EMBODIMENTS

FIGS. 1 to 3 are cross sectional views illustrating a vehicle disc brakeaccording to a first embodiment of the invention. An arrow A indicatesthe direction in which the disc rotor rotates together with wheels inforward travel of a vehicle and a disc exit side and a disc entry side,which will be described below, assume that the vehicle travels forward.

A vehicle disc brake 1 according to the embodiment includes a disc rotor2 rotating together with wheels, a caliper body 3 attached to thevehicle body on one side of the disc rotor 2, and friction pads 4 and 4disposed on both sides of the disc rotor 2.

The caliper body 3 is formed in a six-pot opposed-piston type having amonocoque structure in which a pair of acting parts 3 a and 3 a pushingthe friction pads 4 and 4 is integrally formed with a bridge part 3 bstraddling the outer circumferential side of the disc rotor 2, and threecylinder holes 3 c are formed in each of the acting parts 3 a and 3 a soas to face the three cylinder holes 3 c formed in the other of theacting parts 3 a and 3 a. A piston 5 formed in a cup is movably insertedinto each of the cylinder holes 3 c so that its opening is oriented tothe disc rotor 2. In each of the cylinder holes 3 c, a dust seal 6 a isattached to an inner circumferential part on the opening side, a pistonseal 6 b is attached to the part closer to the bottom of the cylinderhole than the dust seal 6 a, and a hydraulic chamber 7 is definedbetween each of the pistons 5 and each of the cylinder holes 3 c. Inaddition, a torque reception part 3 d with which a disc exit sidesurface 4 a and a disc entry side surface 4 b of the friction pad 4 makecontact is formed in the inner side in the disc radial direction of thedisc rotor side surface of each of the acting parts 3 a. In addition,the bridge part 3 b includes a disc exit side bridge part 3 e disposedon the disc exit side, a disc entry side bridge part 3 f disposed on thedisc entry side, and a central bridge part 3 g disposed in the middle ofthe disc exit side bridge part 3 e and the disc entry side bridge part 3f, and a pad spring 8 for pushing the friction pads 4 and 4 against thedisc inner circumferential side is attached to the central bridge part 3g.

The torque reception parts 3 d have four pad guide grooves 9 facing eachother in each of the side parts of the disc rotor 2. Each of the padguide grooves 9 is formed in a U-shape including a disc radial directionouter side surface 9 a, a disc radial direction inner side surface 9 b,and a facing surface 9 c connecting the disc radial direction outer sidesurface 9 a to the disc radial direction inner side surface 9 b. Inaddition, a caliper side recess 9 d (incorrect installation preventingpart of the invention) concave toward the disc entry side and the outerside in the disc radial direction is formed in the part (close to thecaliper body center) of the disc radial direction outer side surface 9 aof the pad guide groove 9 on the disc entry side and a caliper siderecess 9 e (incorrect installation preventing part of the invention)concave toward the disc exit side and the outer side in the disc radialdirection is formed in the part (close to the caliper body center) ofthe disc radial direction outer side surface 9 a of the pad guide groove9 on the disc exit side.

The friction pads 4 and 4 are disposed between the acting parts 3 a andthe disc rotor 2 and each of the friction pads 4 and 4 includes fourlinings 4 c in slidable contact with the disc rotor 2 and a back plate 4d made of metal on which the linings 4 c are pasted. The back plate 4 dhas a pair of tabs 10 and 11, the tab 10 protruding on the disc entryside, the tab 11 protruding on the disc exit side. A tab side protrusion10 a (incorrect installation preventing part of the invention) that isconvex toward the disc entry side and the outer side in the disc radialdirection and has a shape corresponding to the caliper side recess 9 dis formed in the part (close to the caliper body center) of the discradial direction outer side surface of the tab 10 on the disc entry sidea tab side protrusion 11 a (incorrect installation preventing part ofthe invention) that is convex toward the disc exit side and the outerside in the disc radial direction and corresponds to the caliper siderecess 9 d is formed in the part (close to the caliper body center) ofthe disc radial direction outer side surface of the tab 11 on the discexit side. The friction pads 4 are supported movably in the disc axialdirection by housing the tabs 10 and 11 in the pad guide grooves 9 and 9formed in the caliper body 3 and this omits hanger pins for hanging thefriction pads.

In the vehicle disc brake 1 according to the embodiment formed asdescribed above, as illustrated in FIGS. 1 and 3 , when the frictionpads 4 are installed in the correct state, the tab side protrusions 10 aand 11 a provided on the friction pads 4 and 4 are inserted into thecaliper side recesses 9 d and 9 e formed in the pad guide grooves 9 and9, respectively, so the friction pads 4 and 4 can be installed to thecaliper body 3 movably in the disc axial direction. In contrast, asillustrated in FIG. 2 , when an attempt is made to install the frictionpads 4 and 4 with the disc outer circumferential side and the disc innercircumferential side reversed by mistake, the tab side protrusions 10 aand Ila make contact with the disc radial direction inner side surfaces9 b and 9 b of the pad guide grooves 9 and 9 and the tabs 10 and 11 bumpagainst the disc radial direction outer side surfaces 9 a and 9 a andthe tabs 10 and 11 cannot be inserted into the pad guide grooves 9 and9, thereby preventing the incorrect installation of the friction pads 4and 4.

In the above embodiment, the caliper side recesses are provided in thepad guide grooves and the tab side protrusions are provided on the tabsas the incorrect installation preventing part. Conversely, however, thecaliper side protrusions 9 f, 9 g may be provided in the pad guidegrooves and tab side recesses 10 b, 11 b having shapes corresponding tothe caliper side protrusions may be provided in the tabs (please see,for example, FIGS. 12 and 13 ). In addition, recesses and protrusions asthe incorrect installation preventing part may be formed in the tabs andthe pad guide grooves in either the disc entry side or the disc exitside. In this case, even if an attempt is made to insert the tabs intothe pad guide grooves with the front and the back of the friction padsreversed by mistake, the tabs cannot be inserted into the pad guidegrooves, thereby preventing the incorrect installation of the frictionpads.

FIGS. 4 to 11 illustrate other embodiments of the invention and the samecomponents as in the first embodiment are indicated by the samereference numerals and detailed descriptions are omitted. FIGS. 4 and 5illustrate the second embodiment of the invention, the caliper body 3according to the embodiment is formed by abutting the pair of actingparts 3 a and 3 a against each other via the bridge part 3 b (this hasno problem because the bridge part 3 b is formed by integrating 3 e, 3f, and 3 g) straddling the outer circumferential side of the disc rotor2 and coupling them with a coupling bolt, the caliper body 3 is formedin a four-pot opposed-piston type, and the two cylinder holes 3 c areformed in each of the acting parts 3 a and 3 a so as to face each other.The piston 5 formed in a cup is movably inserted into each of thecylinder holes 3 c with its opening oriented to the disc rotor 2. Inaddition, the torque reception part 3 d with which a disc exit sidesurface 21 b and a disc entry side surface 21 a of a friction pad 21make contact is formed on the inner side in the disc radial direction ofthe disc rotor side surface of each of the acting parts 3 a and thetorque reception part 3 d is provided with four pad guide grooves 22facing each other in the side parts of the disc rotor 2.

Each of the friction pads 21 and 21 includes a lining 21 c in slidablecontact with the disc rotor 2 and a back plate 21 d made of metal onwhich the lining 21 c is pasted, and a pair of tabs 23 and 23 protrudeon the disc entry side and the disc exit side. In addition, a protrusion24 (incorrect installation preventing part of the invention) protrudingto the outer side in the disc rotor circumferential direction is formedat the disc radial direction inner side end of the disc entry sidesurface 21 a of the back plate 21 d.

In the embodiment, as illustrated in FIG. 4 , the protrusion 24 isdisposed on the inner side in the disc radial direction of the inner endin the disc radial direction of the torque reception part 3 d on thedisc entry side of the caliper body 3 when the friction pad 21 isinstalled in the correct state, and the friction pads 21 and 21 can beinstalled to the caliper body 3 movably in the disc axial direction byinserting the tabs 23 and 23 of the friction pads 21 into the pad guidegrooves 22 and 22 of the caliper body 3. In contrast, as illustrated inFIG. 5 , when an attempt is made to install the friction pads 21 and 21with the disc outer circumferential side and the disc innercircumferential side reversed by mistake, the protrusion 24 bumpsagainst the torque reception part 3 d on the disc exit side of thecaliper body and the tabs 23 and 23 cannot be inserted into the padguide grooves 22 and 22, thereby preventing the incorrect installationof the friction pads 21 and 21.

FIGS. 6 and 7 illustrate a third embodiment of the invention, a frictionpad 31 according to the embodiment includes a lining 31 a in slidablecontact with the disc rotor 2 and a back plate 31 b made of metal onwhich the lining 31 a is pasted, and a pair of tabs 32 and 32 protrudeson the disc entry side and the disc exit side. In addition, a pair ofprotrusions 33 and 33 (incorrect installation preventing part of theinvention) protruding to the outer side in the disc rotorcircumferential direction is formed in the disc radial direction innerside end of a disc exit side surface 31 c of the back plate 31 b and thedisc radial direction inner side end of the disc entry side surface 31 dof the back plate 31 b.

In the embodiment, as illustrated in FIG. 6 , when the friction pad 31is installed in the correct state, the protrusions 33 and 33 aredisposed on the inner side in the disc radial direction of the discradial direction inner side end of the both torque reception parts 3 dand 3 d of the caliper body 3, and the friction pads 31 and 31 can beinstalled to the caliper body 3 movably in the disc axial direction byinserting the tabs 32 and 32 of the friction pads 31 into pad guidegrooves 34 and 34 of the caliper body 3. In contrast, as illustrated inFIG. 7 , when an attempt is made to install the friction pads 31 and 31with the disc outer circumferential side and the disc innercircumferential side reversed by mistake, the protrusions 33 and 33 bumpagainst the both torque reception parts 3 d and 3 d of the caliper body3, respectively, and the tabs 32 and 32 cannot be inserted into the padguide grooves 34 and 34, thereby preventing the incorrect installationof the friction pads 31 and 31.

In addition, in the embodiment, even when an attempt is made to insertthe tabs 32 and 32 into the pad guide grooves 34 and 34 with the discouter circumferential side and the disc inner circumferential side ofthe friction pads 31 and 31 revered and the tabs 32 and 32 inclinedobliquely with respect to the caliper body 3, any of the protrusions 33and 33 bumps against the caliper body 3 and incorrect installation canbe surely prevented. In addition, since the pair of protrusions 33 and33 provided in the friction pad 31 protrudes to the outer side in thedisc rotor circumferential direction, the height of the protrusions 33can be suppressed and the amount of exposure of the protrusions 33 and33 from the caliper body 3 can be reduced as compared with theprotrusions 24 of the second embodiment, so the appearance can be keptgood by making the protrusions 33 and 33 inconspicuous.

FIGS. 8 and 9 illustrate a fourth embodiment of the invention and afriction pad 41 according to the embodiment includes a lining 41 a inslidable contact with the disc rotor 2 and a back plate 41 b made ofmetal on which the lining 41 a is pasted, and a pair of tabs 42 and 42protrudes on the disc entry side and the disc exit side. In addition,the back plate 41 b is formed so that a width L1 from a disc exit sidesurface 41 c to a disc entry side surface 41 d on the outer side in thedisc radial direction of the tabs 42 and 42 is smaller than a width L2from a disc exit side surface 41 e to a disc entry side surface 41 f onthe inner side in the disc radial direction.

Torque reception parts 3 h and 3 h provided in the acting parts 3 a and3 a of the caliper body 3 have pad guide grooves 43 and 43 in theintermediate part in the disc radial direction and are formed in a stepin which the length L3 between the torque reception parts 3 h and 3 h,facing each other across the friction pad 41, that are disposed on theouter side in the disc radial direction of the pad guide grooves 43 and43 are smaller than the length L4 between the torque reception parts 3 hand 3 h, facing each other across the friction pad 41, that are disposedon the inner side in the disc radial direction of the pad guide grooves43 and 43 depending on the shape of the back plate 41 b.

In the embodiment, as illustrated in FIG. 8 , when the friction pad 41is installed in the correct state, a small width part on the outer sidein the disc radial direction of the tabs 42 and 42 of the back plate 41b is disposed in the part having a short length between the torquereception parts 3 h and 3 h and a wide width part on the inner side inthe disc radial direction of the tabs 42 and 42 is disposed in the parthaving a long length between the torque reception parts 3 h and 3 h, sothat the friction pads 41 and 41 can be installed to the caliper body 3movably in the disc axial direction by inserting the tabs 42 and 42 intothe pad guide grooves 43 and 43. In contrast, as illustrated in FIG. 9 ,when an attempt is made to install the friction pads 41 and 41 with thedisc outer circumferential side and the disc inner circumferential sidereversed by mistake, a large width part between the disc exit sidesurface 41 e and the disc entry side surface 41 f of the back plate 41 bbumps against the part of the caliper body 3 having a small lengthbetween the torque reception parts 3 h and 3 h and the tabs 42 and 42cannot be inserted into the pad guide grooves 43 and 43, therebypreventing the incorrect installation of the friction pads 41 and 41.

In the invention, the width from the disc exit side surface to the discentry side surface on the inner side in the disc radial direction of thetabs of the back plates of the friction pads may be smaller than thewidth from the disc exit side surface to the disc entry side surface onthe outer side in the disc radial direction of the tabs and, dependingon the shapes of the back plates, the length between the torquereception parts facing each other across the friction pads on the innerside in the disc radial direction of the pad guide grooves may besmaller than the length between the torque reception parts facing eachother across the friction pads on the outer side in the disc radialdirection of the pad guide grooves to form a step.

FIG. 10 indicates a fifth embodiment of the invention, a friction pad 51according to the embodiment includes a lining 51 a in slidable contactwith the disc rotor 2 and a metal back plate 51 b on which the lining 51a is pasted, and a pair of tabs 52 and 52 protrudes on the disc entryside and the disc exit side.

The positions in which the tabs 52 and 52 are formed and the positionsof pad guide grooves 53 and 53 formed in the torque reception parts 3 dand 3 d are determined so that a disc radial direction inner sidesurface 51 c of the friction pad 51 bumps against the central bridgepart 3 g of the caliper body 3 when the friction pad 51 is installedwith the disc inner circumferential side and the disc outercircumferential side reversed by mistake and the tabs 52 and 52 areformed on the outer side in the disc radial direction of the back plate51 b of the friction pad 51 and the pad guide grooves 53 and 53 areformed on the outer side in the disc radial direction of the torquereception part 3 d and 3 d.

In addition, the positions in which the tabs 52 and 52 and the pad guidegrooves 53 and 53 are formed may be present on the inner side in thedisc radial direction to which a disc radial direction outer sidesurface 51 d of the friction pad 51 protrudes from the disc innercircumferential side of the caliper body 3 when the friction pad 51 isinstalled with the disc inner circumferential side and the disc outercircumferential side reversed by mistake. In this case, since thefriction pads are visually identified from the disc innercircumferential side of the caliper body 3 in the case of incorrectinstallation, incorrect installation can be prevented.

The invention is not limited to the above embodiments, which are ofsix-pot or four-pot opposed-piston type, and applicable to two-pot oreight-or-more-pot opposed piston type. In addition, the invention isapplicable regardless of the structure of a caliper body or a frictionpad as long as friction pads can be installed to the caliper bodymovably in the disc axial direction by inserting the tabs of thefriction pads into the pad guide grooves of the caliper body.

REFERENCE SIGNS LIST

-   1: vehicle disc brake-   2: disc rotor-   3: caliper body-   3 a: acting part-   3 b: bridge part-   3 c: cylinder hole-   3 d, 3 h: torque reception part-   3 e: disc exit side bridge part-   3 f: disc entry side bridge part-   3 g: central bridge part-   4: piston-   4 a: disc exit side surface-   4 b: disc entry side surface-   4 c: lining-   4 d: back plate-   5: piston-   6 a: dust seal-   6 b: piston seal-   7: hydraulic chamber-   8: pad spring-   9: pad guide groove-   9 a: disc radial direction outer side surface-   9 b: disc radial direction inner side surface-   9 c: facing surface-   9 d, 9 e: caliper side recess-   10, 11: tab-   10 a, 11 a: tab side protrusion-   21: friction pad-   21 a: disc entry side surface-   21 b: disc exit side surface-   21 c: lining-   21 d: back plate-   22: pad guide groove-   23: tab-   24: protrusion-   31: friction pad-   31 a: lining-   31 b: back plate-   31 c: disc exit side surface-   31 d: disc entry side surface-   32: tab-   33: protrusion-   34: pad guide groove-   41: friction pad-   41 a: lining-   41 b: back plate-   41 c, 41 e: disc exit side surface-   41 d, 41 f: disc entry side surface-   42: tab-   43: pad guide groove-   51: friction pad-   51 a: lining-   51 b: back plate-   51 c: disc radial direction inner side surface-   51 d: disc radial direction outer side surface-   52: tab-   53: pad guide groove

What is claimed is:
 1. A vehicle disc brake comprising: a caliper bodyprovided with an acting part having a cylinder hole open toward a discrotor; and a pair of friction pads disposed on both sides of the discrotor, each of the friction pads having a pair of tabs on a disc entryside and a disc exit side of a back plate in forward travel of avehicle, the friction pads being supported movably in a disc axialdirection by housing the tabs in pad guide grooves formed in the caliperbody, wherein an incorrect installation preventing part is provided soas to prevent incorrect installation by bumping against the caliper bodyor the tabs when the friction pads are installed in the pad guidegrooves in an incorrect orientation, and wherein the incorrectinstallation preventing part is formed by: a caliper side recess or acaliper side protrusion formed in at least one of the pad guide groovesand a tab side protrusion having a shape corresponding to the caliperside recess or a tab side recess having a shape corresponding to thecaliper side protrusion formed in at least one of the tabs correspondingto the at least one of the pad guide grooves, and, when the frictionpads are installed in the incorrect orientation, the caliper sideprotrusion bumps against the at least one of the tabs or the tab sideprotrusion bumps against the at least one of the pad guide grooves.